added listener in flipper plugin for yoga

Summary:
Adds YogaEventListener interface and it's implementation which will be used in flipper for events coming from Yoga
After this diff , we will start getting layout calculate events in flipper listener

Reviewed By: davidaurelio

Differential Revision: D15316928

fbshipit-source-id: da3a53374a52386037b553d460038d988b0162c2

java/com/facebook/yoga/YogaEventListener.java

@@ -0,0 +1,13 @@
+/**
+ * Copyright (c) Facebook, Inc. and its affiliates.
+ *
+ * This source code is licensed under the MIT license found in the LICENSE
+ * file in the root directory of this source tree.
+ */
+package com.facebook.yoga;
+
+public interface YogaEventListener {
+
+  void onLayoutPassEnd(YogaNode node);
+
+}